The invention relates to an imaging system having multiple image capture modes.
Referring to FIG. 1, a digital imaging system 7 may include a digital camera 12 that has an image sensor, or imager 18, to electrically capture an optical image 11. To accomplish this, the imager 18 typically includes an array 13 (see FIG. 2) of photon sensing, pixel sensors 20 that are arranged in a focal plane onto which the image 11 is focused. For an imager that provides linearly encoded indications of the intensities of the captured image (hereinafter called a xe2x80x9clinear imagerxe2x80x9d), during an integration time, or interval, each pixel sensor 20 typically accumulates photons of light energy of a portion, or pixel, of a representation of the image 11 that is focused (by optics in the camera 12) onto the focal plane. At the expiration of the integration interval, each pixel sensor 20 indicates (via an analog voltage, for example) the accumulated charge (for the associated pixel) that, in turn, indicates an intensity of a portion of the pixel area.
The camera 12 typically processes the indications from the pixel sensors 20 to form a frame of digital data (which digitally represents the captured image) and transfers the frame (via a serial bus 15, for example) to a computer 14 for processing. For video, the camera 12 may successively capture several optical images and furnish several frames of data, each of which indicates one of the captured images. The computer 14 may then use the frames to recreate the captured video on a display 9.
Referring to FIG. 2, the sensors 20 may be arranged, for example, in rows and columns. This arrangement allows column 22 and row 24 decoders to selectively retrieve the analog pixel values from the sensors 20 after the capture of the image 11. The decoders 22 and 24 route the selected pixel values to column decoder and signal conditioning circuitry 22 that might include, for example, analog-to-digital converters (ADCs) and circuitry to compensate for noise and/or nonlinearities that are introduced by the sensors 20. The circuitry 22 may furnish the resultant data signals to an input/output (I/O) interface 28 which includes circuitry for interfacing the imager 18 to other circuitry of the camera 12. A control unit 30 may coordinate the above-described activities of the imager 18.
For a linear imager, the duration of the integration interval determines how long the pixel sensors 20 sense, or are exposed to, the optical image 11. In this manner, if the duration of the integration interval is too short, the pixel sensors 20 may be underexposed, and if the duration is too long, the pixel sensors 20 may be overexposed. To set the correct exposure, the camera 12 may control the duration of the integration interval based on the camera""s measurement of the brightness of the optical image 11. In this manner, for bright lighting conditions, the camera 12 typically uses a shorter duration (to prevent overexposure of the pixel sensors 20) than for low lighting conditions (to prevent underexposure of the pixel sensors 20). The camera""s assessment of the brightness may occur, for example, during a calibration, or premetering, mode of the camera 12.
The intensities that are captured by the imager 18 may span a range of available intensity values called an available dynamic range. If the intensity levels are distributed over a large portion of the available dynamic range, then the image appears more vivid than if the intensity levels are distributed over a smaller portion of the available dynamic range.
The type of imager may govern the boundaries of the available dynamic range. For example, the linear imager captures intensities over a dynamic range that is suitable for capturing photographs. Another type of imager may provide logarithmically encoded indications of the intensities of the captured image (hereinafter called a xe2x80x9clogarithmic imagerxe2x80x9d). The logarithmic imager typically captures intensities over a much larger dynamic range than the linear imager.
Due to its ability to capture intensities over a large dynamic range and other factors, a logarithmic imager typically is better suited for object recognition applications (machine vision applications, for example) than the linear imager, and conversely, because of its noise rejection capabilities and other factors, a linear imager typically is better suited to capture photographs than the logarithmic imager. As a result, the two types of imagers typically may not be interchanged for specific applications. Therefore, a camera that uses a logarithmic imager typically is not optimized to take photographs, and a camera that uses a linear imager typically is not optimized for machine vision applications.
Thus, there exists a continuing need for an imaging system to address one or more of the problems stated above.
In one embodiment, a method for use with an array of pixel sensors includes receiving an indication of one of a plurality of image capture modes for the array. The array is configured to be in the indicated mode.
In another embodiment, an imaging system includes an array of pixel sensors and a mode control circuit. The mode control circuit is adapted to receive an indication of one of a set of image capture modes for the array and configure the array based on the indication.
In another embodiment, an imaging system includes an array of pixel sensors and a mode control circuit. The array is adapted to furnish logarithmically encoded indications of light intensities during a first mode and furnish linearly encoded indications of the light intensities during the second mode. The mode control circuit is adapted to selectively place the array in one of the first and second modes.
In yet another embodiment, an imaging system includes at least one array of pixel sensors and a circuit. The circuit is coupled to the array(s) and adapted to receive an indication of a selected image capture mode out of a group of image capture modes and use the array(s) to provide second indications of an image captured in accordance with the selected image capture mode.